Method of processing target object

ABSTRACT

A plasma processing method can suppress both surface roughness of a wiring and surface roughness of a metal mask. The method includes generating plasma of a first processing gas containing a fluorocarbon gas and/or a hydrofluorocarbon gas to etch a diffusion barrier film until a copper wiring is exposed and generating plasma of a second processing gas containing a carbon-containing gas to form an organic film on a surface of a target object in which the diffusion barrier film is etched.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Japanese Patent Application No.2015-185167 filed on Sep. 18, 2015, the entire disclosures of which areincorporated herein by reference.

TECHNICAL FIELD

The embodiments described herein pertain generally to a method ofprocessing a target object; and, more particularly, to a methodincluding a process performed on the target object before the targetobject is transferred into an atmospheric environment in the manufactureof a multilayer wiring structure.

BACKGROUND

A multilayer wiring structure may be used as a wiring structure of anelectronic component. The multilayer wiring structure includes, forexample, a first wiring layer, a diffusion barrier film and a secondwiring layer. The first wiring layer includes an insulating film and acopper wiring, and the copper wiring is formed within a trench which isformed in the insulating film. The diffusion barrier film is provided onthe first wiring layer. The second wiring layer is provided on thediffusion barrier film. The second wiring layer includes an insulatingfilm and a copper wiring. The copper wiring of the second wiring layeris formed within a trench and a via hole which are formed in theinsulating film of the second wiring layer. The copper wiring of thesecond wiring layer is connected to the copper wiring of the firstwiring layer through an opening formed in the diffusion barrier film.

A damascene method is used to manufacture this multilayer wiringstructure. By way of example, in a dual damascene method, a diffusionbarrier film and an insulating film are formed on a first wiring layerof a target object. Then, a resist mask provided with an opening isformed on the insulating film, and a trench and a via hole is thenformed in the insulating film by plasma etching. Subsequently, anopening is formed in the diffusion barrier film by plasma etching. Thisopening is connected to the via hole and extended down to a surface of acopper wiring of the first wiring layer. After the opening is formed inthe diffusion barrier film, the target object is transferred into anatmospheric environment. Thereafter, a wet cleaning process is performedon the target object, and copper is filled in the trench, the via holeand the opening of the diffusion barrier film.

In the plasma etching of the diffusion barrier film by using thedamascene method, a processing gas containing fluorine is generallyused. In the plasma etching with this processing gas, if the opening isformed in the diffusion barrier film and the copper wiring of the firstwiring layer is exposed, the surface of the copper wiring is exposed toactive species of the fluorine. As a result, copper fluoride is formedon the surface of the copper wiring of the first wiring layer. If thecopper fluoride comes into contact with moisture under the atmosphericenvironment, a hydrate is generated. Accordingly, surface roughness ofthe copper wiring is generated.

As a technique to deal with the surface roughness of the copper wiring,a technique of reducing the copper fluoride by performing a plasmaprocess with a nitrogen gas and a hydrogen gas before the target objectis transferred into the atmospheric environment and after the plasmaetching of the diffusion barrier film is conducted is described inPatent Document 1.

Patent Document 1: Japanese Patent Laid-open Publication No. 2006-156486

In this technique, it is required to use a metal mask made of, forexample, Ti or TiN instead of the resist mask which is typically used inthe manufacture of the multilayer wiring structure. If, however, theplasma process with the nitrogen gas and the hydrogen gas is performedafter the plasma etching of the diffusion barrier film is conducted and,then, if the target object is transferred into the atmosphericenvironment, the metal mask becomes to have surface roughness. Thissurface roughness of the metal mask is also deemed to be caused by acontact between the target object and moisture in the atmosphericenvironment. In this regard, it is required to suppress both the surfaceroughness of the copper wiring and the surface roughness of the metalmask.

SUMMARY

In one exemplary embodiment, a method of processing a target objectincludes (i) preparing the target object, including a wiring layerhaving a first insulating film and a copper wiring formed in the firstinsulating film, a diffusion barrier film provided on the wiring layer,a second insulating film provided on the diffusion barrier film and ametal mask which is provided on the second insulating film and providedwith an opening, in which a portion of the second insulating filmexposed through the opening is etched; (ii) generating plasma of a firstprocessing gas containing a fluorocarbon gas and/or a hydrofluorocarbongas to etch the diffusion barrier film until the copper wiring isexposed (hereinafter, referred to as “first process”); and (iii)generating plasma of a second processing gas containing acarbon-containing gas to form an organic film on a surface of the targetobject in which the diffusion barrier film is etched (hereinafter,referred to as “second process”).

In the method according to the exemplary embodiment, the organic film isformed on the surface of the target object in the second process afteretching the diffusion barrier film in the first process. The targetobject is transferred into an atmospheric environment after the secondprocess is performed. At this time, a surface of the copper wiring and asurface of the metal mask are protected from moisture in the atmosphereby the organic film. Therefore, according to this method, both surfaceroughness of the copper wiring and surface roughness of the metal maskcan be suppressed.

The carbon-containing gas may be a hydrocarbon gas. The organic filmformed by the hydrocarbon gas hardly contains fluorine. Accordingly,this organic film has a high wetting property, i.e., a small contactangle with respect to a cleaning liquid used in wet cleaning. Therefore,this organic film is easily removed by the wet cleaning.

When the carbon-containing gas is the hydrocarbon gas, a processing gasnot containing a hydrogen gas may be used as the second processing gas.The hydrogen gas is a source of active species of hydrogen having aneffect of reducing the organic film. Since the second processing gasdoes not contain the hydrogen gas, the organic film can be formedefficiently.

The carbon-containing gas may be a fluorocarbon gas, and the secondprocessing gas may further contain a hydrogen gas. In this exemplaryembodiment, the fluorocarbon gas serves as a carbon source of theorganic film, and the hydrogen gas has a function of reducing fluorinein the organic film. Therefore, according to this exemplary embodiment,the organic film having a small amount of fluorine is formed. Since thisorganic film has the high wetting property, i.e., the small contactangle with respect to the cleaning liquid used in the wet cleaning, theorganic film can be easily removed by the wet cleaning.

When the second processing gas contains a fluorocarbon gas and ahydrogen gas, a flow rate of the hydrogen gas may be set to be 5 timesto 20 times as large as a flow rate of the fluorocarbon gas contained inthe second processing gas. According to the present exemplaryembodiment, it is possible to form the organic film having a higherwetting property for the cleaning liquid used in the wet cleaning.

A temperature of the target object may be maintained at 60° C. or lessin the second process. In a high temperature environment equal to orhigher than, e.g., 300° C., thermal decomposition of the organic filmoccurs. Since, however, the temperature of the target object in thesecond process is maintained at 60° C. or less, the organic film can beformed efficiently.

The organic film having a film thickness equal to or larger than 2 nmmay be formed in the second process. With the organic film having such afilm thickness, it may be possible to suppress the moisture in theatmosphere from being contacted with the organic film.

The fluorocarbon gas contained in the second processing gas may containone or more of a C₄F₈ gas, a C₄F₆ gas and a C₅F₈ gas. Further, the firstprocessing gas may contain one or more of a CF₄ gas, a CHF₃ gas, a C₄F₈gas, a C₄F₆ gas, a CH₂F₂ gas and a CH₃F gas. The diffusion barrier filmmay include a single-layered film made of SiC, SiCN or SiN, or amulti-layered film including a plurality of films each of which is madeof SiC, SiCN or SiN. The second insulating film may include asingle-layered film made of SiOCH, a multi-layered film including a filmmade of SiO₂ and a low dielectric constant film, or a multi-layered filmincluding a plurality of low dielectric constant films. The metal maskmay be made of Ti or TiN.

The target object may be kept accommodated in a processing vessel of asingle plasma processing apparatus over a period during which the firstprocess is performed and a period during which the second process isperformed.

According to the exemplary embodiment as described above, both thesurface roughness of the copper wiring and the surface roughness of themetal mask can be suppressed.

The foregoing summary is illustrative only and is not intended to be inany way limiting. In addition to the illustrative aspects, embodiments,and features described above, further aspects, embodiments, and featureswill become apparent by reference to the drawings and the followingdetailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

In the detailed description that follows, embodiments are described asillustrations only since various changes and modifications will becomeapparent to those skilled in the art from the following detaileddescription. The use of the same reference numbers in different figuresindicates similar or identical items.

FIG. 1 is a flowchart for describing a method of processing a targetobject according to an exemplary embodiment;

FIG. 2 is a cross sectional view illustrating the target object on whichthe method of FIG. 1 is performed;

FIG. 3 is a diagram schematically illustrating an example of a substrateprocessing system and a cleaning apparatus in which the method of FIG. 1is performed;

FIG. 4 is a diagram schematically illustrating an example of a plasmaprocessing apparatus in which the method of FIG. 1 is performed;

FIG. 5 is a flowchart for describing a process ST1 shown in FIG. 1;

FIG. 6 is an enlarged cross sectional view illustrating a part of thetarget object in the course of performing the method of FIG. 1;

FIG. 7 is an enlarged cross sectional view illustrating a part of thetarget object in the course of performing the method of FIG. 1;

FIG. 8 is an enlarged cross sectional view illustrating a part of thetarget object in the course of performing the method of FIG. 1;

FIG. 9 is an enlarged cross sectional view illustrating a part of thetarget object in the course of performing the method of FIG. 1;

FIG. 10 is an enlarged cross sectional view illustrating a part of thetarget object in the course of performing the method of FIG. 1;

FIG. 11 is an enlarged cross sectional view illustrating a part of thetarget object in the course of performing the method of FIG. 1;

FIG. 12 is an enlarged cross sectional view illustrating a part of thetarget object in the course of performing the method of FIG. 1; and

FIG. 13 is an enlarged cross sectional view illustrating a part of thetarget object in the course of performing the method of FIG. 1.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings, which form a part of the description. In thedrawings, similar symbols typically identify similar components, unlesscontext dictates otherwise. Furthermore, unless otherwise noted, thedescription of each successive drawing may reference features from oneor more of the previous drawings to provide clearer context and a moresubstantive explanation of the current exemplary embodiment. Still, theexemplary embodiments described in the detailed description, drawings,and claims are not meant to be limiting. Other embodiments may beutilized, and other changes may be made, without departing from thespirit or scope of the subject matter presented herein. It will bereadily understood that the aspects of the present disclosure, asgenerally described herein and illustrated in the drawings, may bearranged, substituted, combined, separated, and designed in a widevariety of different configurations, all of which are explicitlycontemplated herein.

FIG. 1 is a flowchart for describing a method of processing a targetobject according to an exemplary embodiment. Particularly, the method MTshown in FIG. 1 includes processes which are performed on the targetobject before the target object is transferred into an atmosphericenvironment in the manufacture of a multilayer wiring structure.

FIG. 2 is a cross sectional view illustrating an example of the targetobject on which the method of FIG. 1 is performed. The target object(hereinafter, referred to as “wafer W”) shown in FIG. 2 is obtained inthe course of manufacturing the multilayer wiring structure by using adual damascene method. The wafer W has a wiring layer WL. The wiringlayer WL includes a first insulating film IS1, a barrier metal film BLand a copper wiring CW. Further, the wafer W also includes a diffusionbarrier film DL, a second insulating film IS2, an oxide film OX, a metalmask MK, an organic layer OL, an antireflection film AL and a resistmask RM.

The first insulating film IS1 is made of an insulating material and/or alow-dielectric constant material. The first insulating film IS1 may beimplemented by, by way of example, but not limitation, a single-layeredfilm made of SiOCH, a multi-layered film including a film made of SiO₂and a low dielectric constant film, or a multi-layered film including amultiple number of low dielectric constant films. The first insulatingfilm IS1 has a trench formed therein. The copper wiring CW is buried inthe trench of the first insulating film IS1. The barrier metal film BLis made of a metal such as, but not limited to, Ta, and is providedbetween a surface of the first insulating film IS1 forming the trenchand the copper wiring CW.

The diffusion barrier film DL is provided on the wiring layer WL. Thediffusion barrier film DL may be made of, by way of non-limitingexample, SiC, SiCN or SiN. Further, the diffusion barrier film DL may beimplemented by a multi-layered film having a multiple number of filmseach of which is made of SiC, SiCN or SiN.

The second insulating film IS2 is provided on the diffusion barrier filmDL. The second insulating film IS2 is made of an insulating materialand/or a low dielectric constant material. By way of example, the secondinsulating film IS2 may be implemented by, by way of example, but notlimitation, a single-layered film made of SiOCH, a multi-layered filmincluding a film made of SiO₂ and a low dielectric constant film, or amulti-layered film including a multiple number of low dielectricconstant films.

The oxide film OX is provided on the second insulating film IS2. Theoxide film OX may be a silicon oxide film made of, e.g., TEOS. The metalmask MK is provided on the oxide film OX. The metal mask MK has apattern which is to be transcribed into the second insulating film IS2.That is, the metal mask MK is provided with an opening corresponding toa trench which is to be formed in the second insulating film IS2. Themetal mask MK may be made of, e.g., titanium (Ti) or titanium nitride(TiN).

The organic layer OL is formed to cover the metal mask MK and to fillthe opening of the metal mask MK. The antireflection film AL is providedon the organic layer OL. The resist mask RM is provided on theantireflection film AL. The resist mask RM has a pattern which is to betranscribed into the second insulating film IS2. That is, the resistmask RM is provided with an opening corresponding to a via hole which isto be formed in the second insulating film IS2.

FIG. 3 is a diagram schematically illustrating a substrate processingsystem in which the method of FIG. 1 is performed. The substrateprocessing system 110 shown in FIG. 3 includes a loader module 112, aload lock module 141, a load lock module 142, a transfer module 116 anda multiple number of process modules 181 to 184.

The loader module 112 is an apparatus configured to transfer a substratein an atmospheric environment. The loader module 112 is equipped with aplurality of tables 120. FOUP 122 configured to accommodate a multiplenumber of wafers therein is mounted on each of the tables 120. Withinthe FOUP 122, the wafers are placed in an atmospheric environment.

The loader module 112 has therein a transfer chamber 112 c, and atransfer robot 112 r is provided in the transfer chamber 112 c. Theloader module 112 is connected to the load lock module 141 and the loadlock module 142. The transfer robot 112 r is configured to transfer thesubstrate between the FOUP 122 and the load lock module 141 or betweenthe FOUP 122 and the load lock module 142.

The load lock module 141 and the load lock module 142 include a chamber141 c and a chamber 142 c for preliminary decompression, respectively.The load lock module 141 and the load lock module 142 are connected tothe transfer module 116. The transfer module 116 includes a transferchamber 116 c which can be decompressed, and a transfer robot 116 r isprovided within the transfer chamber 116 c. A multiple number of processmodules 181 to 184 are connected to the transfer module 116. Thetransfer robot 116 r of the transfer module is configured to transferthe substrate between any one of the load lock modules 141 and 142 andany one of the multiple number of process modules 181 to 184 and, also,between any two of the multiple number of process modules 181 to 184.

Each of the process modules 181 to 184 is a substrate processingapparatus configured to perform a dedicated process on the substrate.One of the process modules 181 to 184 is implemented by a plasmaprocessing apparatus 10 shown in FIG. 4.

FIG. 4 is a diagram schematically illustrating an example of a plasmaprocessing apparatus in which the method of FIG. 1 is performed. Theplasma processing apparatus 10 depicted in FIG. 4 is configured as acapacitively coupled plasma processing apparatus, and includes asubstantially cylindrical processing vessel 12. The processing vessel 12is made of, by way of non-limiting example, aluminum having ananodically oxidized inner wall surface. The processing vessel 12 isframe-grounded.

A substantially cylindrical supporting member 14 is provided on a bottomportion of the processing vessel 12. The supporting member 14 is madeof, by way of example, but not limitation, an insulating material.Within the processing vessel 12, the supporting member 14 is verticallyextended from the bottom portion of the processing vessel 12. Further, amounting table PD is provided within the processing vessel 12. Themounting table PD is supported on the supporting member 14.

The mounting table PD is configured to hold the wafer W on a surfacethereof. The mounting table PD includes a lower electrode LE and anelectrostatic chuck ESC. The lower electrode LE includes a first plate18 a and a second plate 18 b. Each of the first plate 18 a and thesecond plate 18 b is made of a metal such as, but not limited to,aluminum, and substantially has a disk shape. The second plate 18 b isprovided on the first plate 18 a, and is electrically connected to thefirst plate 18 a.

The electrostatic chuck ESC is provided on the second plate 18 b. Theelectrostatic chuck ESC has a structure in which an electrode made of aconductive film is embedded between a pair of insulating layers orinsulating sheets. The electrode of the electrostatic chuck ESC iselectrically connected to a DC power supply 22 via a switch 23. Theelectrostatic chuck ESC is configured to attract and hold the wafer W byan electrostatic force such as a Coulomb force generated by a DC voltageapplied from the DC power supply 22. Accordingly, the electrostaticchuck ESC is capable of holding the wafer W thereon.

A focus ring FR is disposed on a peripheral portion of the second plate18 b to surround an edge of the wafer W and the electrostatic chuck ESC.This focus ring FR is provided to improve uniformity of the plasmaprocess performed on the wafer. The focus ring FR is made of a materialwhich is appropriately selected depending on the plasma processinvolved. By way of non-limiting example, the focus ring FR may be madeof quartz.

A coolant path 24 is provided within the second plate 18 b. The coolantpath 24 constitutes a temperature control device. A coolant is suppliedinto the coolant path 24 from a chiller unit provided outside theprocessing vessel 12 via a pipeline 26 a. The coolant supplied into thecoolant path 24 is returned back into the chiller unit via a pipeline 26b. With this configuration, the coolant is circulated between thecoolant path 24 and the chiller unit. By controlling a temperature ofthe coolant, a temperature of the wafer W held on the electrostaticchuck ESC is controlled.

Further, the plasma processing apparatus 10 is equipped with a gassupply line 28. Through the gas supply line 28, a heat transfer gas, forexample, a He gas, is supplied from a heat transfer gas supply deviceinto a gap between a top surface of the electrostatic chuck ESC and arear surface of the wafer W.

Further, the plasma processing apparatus 10 includes an upper electrode30. The upper electrode 30 is provided above the mounting table PD.Formed between the upper electrode 30 and the mounting table PD is aprocessing space S in which the plasma process is performed on the waferW.

The upper electrode 30 is supported at an upper portion of theprocessing vessel 12 with an insulating shield member 32 therebetween.The upper electrode 30 may include a ceiling plate 34 and a supportingbody 36. The ceiling plate 34 directly faces the processing space S, andis provided with a multiple number of gas discharge holes 34 a. In theexemplary embodiment, the ceiling plate 34 is formed of silicon.

The supporting body 36 is configured to support the ceiling plate 34 ina detachable manner, and is made of a conductive material such as, butnot limited to, aluminum. The supporting body 36 may have awater-cooling structure. A gas diffusion space 36 a is formed within thesupporting body 36. Multiple gas through holes 36 b are extendeddownwards from the gas diffusion space 36 a, and these gas through holes36 b communicate with the gas discharge holes 34 a, respectively.Further, the supporting body 36 is also provided with a gas inletopening 36 c through which a processing gas is introduced into the gasdiffusion space 36 a, and this gas inlet opening 36 c is connected to agas supply line 38.

The gas supply line 38 is connected to a gas source group 40 via a valvegroup 42 and a flow rate controller group 44. The gas source group 40includes a plurality of gas sources. As an example, the gas source group40 includes one or more sources of a fluorocarbon gas, one or moresources of a hydrofluorocarbon gas, a source of a hydrocarbon gas, asource of a rare gas, a source of a nitrogen gas (N₂ gas), a source of ahydrogen gas (H₂ gas) and one or more sources of an oxygen-containinggas. The one or more sources of the fluorocarbon gas may include, butnot limited to, a source of a C₄F₈ gas, a source of a CF₄ gas, a sourceof a C₄F₆ gas, and a source of a C₅F₈ gas. The one or more sources ofthe hydrofluorocarbon gas may include, but not limited to, a source of aCHF₃ gas, a source of a CH₂F₂ gas and a source of a CH₃F gas. The sourceof the hydrocarbon gas may be, for example, a source of a CH₄ gas, aC₂H₂ gas, a C₂H₄ gas, a C₂H₆ gas, a C₃H₄ gas, a C₃H₆ gas, a C₃H₈ gas, aC₄H₄ gas, a C₄H₆ gas, a C₄H₈ gas or a C₄H₁₀ gas. The source of the raregas may be a source of a rare gas such as a He gas, a Ne gas, an Ar gas,a Kr gas or a Xe gas. Here, as an example, the source of the rare gasmay be a source of an Ar gas. The one or more sources of theoxygen-containing gas may include a source of an oxygen gas (O₂ gas).Further, the one or more sources of the oxygen-containing gas mayfurther include a source of a CO gas and/or a source of a CO₂ gas.

The valve group 42 includes a multiple number of valves, and the flowrate controller group 44 includes a multiple number of flow ratecontrollers such as mass flow controllers. Each of the gas sourcesbelonging to the gas source group 40 is connected to the gas supply line38 via each corresponding valve belonging to the valve group 42 and eachcorresponding flow rate controller belonging to the flow rate controllergroup 44.

Further, in the plasma processing apparatus 10, a deposition shield 46is provided along an inner wall of the processing vessel 12 in adetachable manner. The deposition shield 46 is also provided on an outerside surface of the supporting member 14. The deposition shield 46 isconfigured to suppress an etching byproduct from adhering to a wallsurface of the processing vessel 12 such as an inner wall surfacethereof, and is formed by coating an aluminum member with ceramics suchas Y₂O₃.

At the bottom side of the processing vessel 12, a gas exhaust plate 48having a multiple number of through holes is provided between thesupporting member 14 and a side wall of the processing vessel 12. Thegas exhaust plate 48 may be made of, by way of example, an aluminummember coated with ceramics such as Y₂O₃. The processing vessel 12 isalso provided with a gas exhaust opening 12 e under the gas exhaustplate 48. The gas exhaust opening 12 e is connected with a gas exhaustdevice 50 via a gas exhaust line 52. The gas exhaust device 50 includesa vacuum pump such as a turbo molecular pump, and is capable ofdecompressing the space within the processing vessel 12 to a requiredvacuum level. Further, a carry-in/out opening 12 g for the wafer W isprovided at the side wall of the processing vessel 12, and thecarry-in/out opening 12 g is opened or closed by a gate valve 54.

Furthermore, the plasma processing apparatus 10 includes a first highfrequency power supply 62 and a second high frequency power supply 64.The first high frequency power supply 62 is configured to generate afirst high frequency power for plasma generation having a frequency inthe range from, for example, 27 MHz to 100 MHz. The first high frequencypower supply 62 is connected to the lower electrode LE via a matchingdevice 66. The matching device 66 includes a circuit configured to matchan output impedance of the first high frequency power supply 62 and animpedance at a load side. Further, the first high frequency power supply62 may be connected to the upper electrode 30 via the matching device66.

The second high frequency power supply 64 is configured to generate asecond high frequency power for bias, that is, for ion attraction intothe wafer W. For example, the second high frequency power supply 64generates the second high frequency power having a frequency in therange from 400 kHz to 13.56 MHz. The second high frequency power supply64 is connected to the lower electrode LE via a matching device 68. Thematching device 68 includes a circuit configured to match an outputimpedance of the second high frequency power supply 64 and an impedanceat a load side.

Furthermore, the plasma processing apparatus 10 further includes a powersupply 70. The power supply 70 is connected to the upper electrode 30.The power supply 70 is configured to apply, to the upper electrode 30, avoltage for attracting positive ions in the processing space S into theceiling plate 34. As an example, the power supply 70 is a DC powersupply configured to generate a negative DC voltage. As another example,the power supply 70 may be an AC power supply configured to generate analternating current voltage having a relatively low frequency.

Further, in the exemplary embodiment, the plasma processing apparatus 10may further include a control unit Cnt. The control unit Cnt isimplemented by a computer including a processor, a storage unit, aninput device, a display device, and so forth, and is configured tocontrol individual components of the plasma processing apparatus 10. Inthe control unit Cnt, an operator can input commands through the inputdevice to manage the plasma processing apparatus 10, and an operationalstatus of the plasma processing apparatus 10 can be visually displayedon the display device. Further, the storage unit of the control unit Cntstores therein a control program for controlling various processesperformed in the plasma processing apparatus 10 by the processor, or aprogram for allowing each component of the plasma processing apparatus10 to perform a process according to processing conditions, i.e., aprocess recipe.

Now, referring back to FIG. 1, the method MT will be elaborated. Thefollowing description will be provided for an example case where thewafer W shown in FIG. 2 is processed in the substrate processing system110 including the plasma processing apparatus 10 shown in FIG. 4 as oneof the process modules. In the following description, reference is madeto FIG. 6 to FIG. 13. FIG. 6 to FIG. 13 are enlarged cross sectionalviews illustrating a part of the target object in the course ofperforming the method of FIG. 1.

First, in the method MT, the wafer W as shown in FIG. 2 is carried intothe processing vessel 12 of the plasma processing apparatus 10 as theprocess module via the loader module 112, either one of the load lockmodules 141 and 142 and the transfer module 116 from the FOUP 122. Thewafer W carried into the processing vessel 12 is mounted on the mountingtable PD, and is held on the mounting table PD.

In the method MT, a process ST1 is performed. In the process ST1, awafer on which a subsequent process ST2 to be described layer will beperformed is prepared. In the process ST1, the antireflection film AL,the organic layer OL, the oxide film OX and the second insulating filmS12 are etched. Below, the process ST1 will be discussed in detail. FIG.5 is a flowchart for describing the process ST1.

As depicted in FIG. 5, the process ST1 includes a process ST1 a to aprocess ST1 f. In the process ST1, the process ST1 a is first performed.In the process ST1 a, a portion of the antireflection film AL exposedthrough an opening MO of the resist mask RM is etched. For the purpose,in the process ST1 a, a processing gas is supplied into the processingvessel 12 from a gas source selected from the gas sources belonging tothe gas source group 40. This processing gas may contain, by way ofexample, but not limitation, a fluorocarbon gas, a hydrofluorocarbon gasand an oxygen gas. By way of non-limiting example, a CF₄ gas may be usedas the fluorocarbon gas. Further, the hydrofluorocarbon gas may be, butnot limited to, a CHF₃ gas. Furthermore, in the process ST1 a, the gasexhaust device 50 is operated, and an internal pressure of theprocessing vessel 12 is regulated to a preset pressure. In addition, inthe process ST1 a, the first high frequency power from the first highfrequency power supply 62 and the second high frequency power from thesecond high frequency power supply 64 are supplied to the lowerelectrode LE.

In the process ST1 a, plasma of the processing gas is generated, and theportion of the antireflection film AL exposed through the opening MO ofthe resist mask RM is etched. As a result, as illustrated in FIG. 6, theportion of the antireflection film AL exposed through the opening MO ofthe resist mask RM is removed, so that an opening MO1 is formed in theantireflection film AL. Further, the above-described operations of theindividual components of the plasma processing apparatus 10 in theprocess ST1 a may be controlled by the control unit Cnt.

Subsequently, in the process ST1, a process ST1 b is performed. In theprocess ST1 b, the organic layer OL is etched. For the purpose, in theprocess ST1 b, a processing gas is supplied into the processing vessel12 from a gas source selected from the gas sources belonging to the gassource group 40. As an example of the process ST1 b, a processing gascontaining an oxygen gas and a carbon monoxide gas is supplied into theprocessing vessel 12, and, subsequently, a processing gas containing ahydrogen gas and a nitrogen gas is supplied into the processing vessel12. Further, in the process ST1 b, the gas exhaust device 50 isoperated, and the internal pressure of the processing vessel 12 isregulated to a set pressure. Further, in the process ST1 b, the firsthigh frequency power is supplied to the lower electrode LE from thefirst high frequency power supply 62.

In the process ST1 b, plasma of the processing gases is generated, and aportion of the organic layer OL exposed through the opening MO1 isetched. Further, the resist mask RM is also etched. As a result, asdepicted in FIG. 7, the portion of the organic layer OL exposed throughthe opening MO1 is removed, so that an opening MO2 is formed in theorganic layer OL. Further, the above-described operations of theindividual components of the plasma processing apparatus 10 in theprocess ST1 b may be controlled by the control unit Cnt.

Subsequently, in the process ST1, a process ST1 c is performed. In theprocess ST1 c, the oxide film OX and the second insulating film IS2 areetched. For the purpose, a processing gas is supplied into theprocessing vessel 12 from a gas source selected from the gas sourcesbelonging to the gas source group 40. As an example of the process ST1c, a processing gas containing a fluorocarbon gas is supplied into theprocessing vessel 12, and a processing gas containing ahydrofluorocarbon gas, a nitrogen gas and an oxygen gas is then suppliedinto the processing vessel 12. As the fluorocarbon gas, a CF₄ gas and aC₄F₈ gas may be used, for example. Further, as the hydrofluorocarbongas, a CH₂F₂ gas may be used, for example. Further, in the process ST1c, the gas exhaust device 50 is operated, and the internal pressure ofthe processing vessel 12 is set to a predetermined pressure.Furthermore, in the process ST1 c, the first high frequency power fromthe first high frequency power supply 62 and the second high frequencypower from the second high frequency power supply 64 are supplied to thelower electrode LE.

In the process ST1 c, plasma of the processing gases is generated, andthe oxide film OX and the second insulating film IS2 are etched. Here,the second insulating film IS2 is etched up to a midway portion in afilm thickness direction thereof. Further, in the process ST1 c, theantireflection film AL is also etched. As a result, as illustrated inFIG. 8, portions of the oxide film OX and the second insulating film IS2exposed through the opening MO2 are removed, so that an opening MO3 isformed in the oxide film OX and the second insulating film IS2.Furthermore, in the process ST1 c, the antireflection film AL isremoved, and a film thickness of the organic layer OL is slightlyreduced. In addition, the above-described operations of the individualcomponents of the plasma processing apparatus 10 in the process ST1 cmay be controlled by the control unit Cnt.

Thereafter, in the process ST1, a process ST1 d is performed. In theprocess ST1 d, the organic layer OL is removed. For the purpose, aprocessing gas is supplied into the processing vessel 12 from a gassource selected from the gas sources belonging to the gas source group40. This processing gas may contain a carbon dioxide gas. Further, inthe process ST1 d, the gas exhaust device 50 is operated, and theinternal pressure of the processing vessel 12 is set to a predeterminedpressure. Furthermore, in the process ST1 d, the first high frequencypower is supplied to the lower electrode LE from the first highfrequency power supply 62.

In the process ST1 d, plasma of the processing gas is generated, andaching of the organic layer OL is performed. As a consequence, asdepicted in FIG. 9, the organic layer OL is removed, so that a metalmask MK is exposed. The metal mask MK provided with an opening TO havinga width larger than that of the opening MO3. Further, theabove-described operations of the individual components of the plasmaprocessing apparatus 10 in the process ST1 d may be controlled by thecontrol unit Cnt.

Subsequently, in the process ST1, a process ST1 e is performed. In theprocess ST1 e, the oxide film OX is etched. For the purpose, aprocessing gas is supplied into the processing vessel 12 from a gassource selected from the gas sources belonging to the gas source group40. This processing gas may contain a fluorocarbon gas, ahydrofluorocarbon gas and a rare gas. The fluorocarbon gas may be, forexample, a CF₄ gas. Further, the hydrofluorocarbon gas may be, by way ofexample, but not limitation, a CHF₃ gas. Further, in the process ST1 e,the gas exhaust device 50 is operated, and the internal pressure of theprocessing vessel 12 is set to a predetermined pressure. In addition, inthe process ST1 e, the first high frequency power from the first highfrequency power supply 62 and the second high frequency power from thesecond high frequency power supply 64 are supplied to the lowerelectrode LE.

In the process ST1 e, plasma of the processing gas is generated, and aportion of the oxide film OX exposed through the opening TO is etched.As a result, as depicted in FIG. 10, the portion of the oxide film OXexposed through the opening TO is removed. Further, the above-describedoperations of the individual components of the plasma processingapparatus 10 in the process ST1 e may be controlled by the control unitCnt.

Then, in the process ST1, the process ST1 f is conducted. In the processST1 f, the second insulating film IS2 is further etched. For thepurpose, a processing gas is supplied into the processing vessel 12 froma gas source selected from the gas sources belonging to the gas sourcegroup 40. This processing gas may contain a fluorocarbon gas, a raregas, a nitrogen gas and an oxygen gas. The fluorocarbon gas may be, forexample, a CF₄ gas and a C₄F₈ gas. Further, in the process ST1 f, thegas exhaust device 50 is operated, and the internal pressure of theprocessing vessel 12 is set to a predetermined pressure. In addition, inthe process ST1 f, the first high frequency power from the first highfrequency power supply 62 and the second high frequency power from thesecond high frequency power supply 64 are supplied to the lowerelectrode LE.

In the process ST1 f, plasma of the processing gas is generated, and thesecond insulating film IS2 is further etched. To elaborate, a portion ofthe second insulating film IS2 exposed through the opening TO and aportion of the second insulating film IS2 exposed through the openingMO3 are etched. As a result, as depicted in FIG. 11, a trench TR and avia hole VH are formed in the second insulating film IS2. Furthermore,the above-described operations of the individual components of theplasma processing apparatus 10 in the process ST1 f may be controlled bythe control unit Cnt.

Referring back to FIG. 1, after the process ST1 is ended, a process ST2is performed in the method MT. In the process ST2, plasma of aprocessing gas (first processing gas) containing a fluorocarbon gasand/or a hydrofluorocarbon gas is generated in order to etch thediffusion barrier film DL until the copper wiring CW is exposed. For thepurpose, the processing gas is supplied into the processing vessel 12from a gas source selected from the gas sources belonging to the gassource group 40. This processing gas may contain one or more of aCF₄gas, a CHF₃ gas, a C₄F₈ gas, a C₄F₆ gas, a CH₂F₂ gas and a CH₃F gas.Further, this processing gas may further contain a rare gas, a nitrogengas and an oxygen gas. By way of example, this processing gas maycontain a CF₄ gas, a C₄F₈ gas, an Ar gas, a nitrogen gas and an oxygengas. Further, in the process ST2, the gas exhaust device 50 is operated,and the internal pressure of the processing vessel 12 is set to apredetermined pressure. Further, in the process ST2, the first highfrequency power from the first high frequency power supply 62 and thesecond high frequency power from the second high frequency power supply64 are supplied to the lower electrode LE.

In the process ST2, the plasma of the processing gas is generated, andthe diffusion barrier film DL is etched. As a result, as depicted inFIG. 12, the via hole VH is extended to a surface of the copper wiringCW. After the process ST2 is conducted, copper on the surface of thecopper wiring CW is turned into copper fluoride. Further, a reactionproduct made of, by way of example, SiF₄ is deposited on the metal maskMK. The above-described operations of the individual components of theplasma processing apparatus 10 in the process ST2 may be controlled bythe control unit Cnt.

Thereafter, in the method MT, a process ST3 is performed. In the processST3, plasma of a processing gas (second processing gas) containing acarbon-containing gas is generated. For the purpose, the processing gasis supplied into the processing vessel 12 from a gas source selectedfrom the gas sources belonging to the gas source group 40. Further, inthe process ST3, the gas exhaust device 50 is operated, and the internalpressure of the processing vessel 12 is set to a predetermined pressure.Further, in the process ST3, the first high frequency power from thefirst high frequency power supply 62 and the second high frequency powerfrom the second high frequency power supply 64 is supplied to the lowerelectrode LE.

In the process ST3, the plasma of the processing gas is generated, andan organic film OM is formed on a surface of the wafer W, as illustratedin FIG. 13. Further, in the process ST3, the amount of the copperfluoride and the amount of the reaction product on the metal mask MK arereduced. Further, in the process ST3, the above-described operations ofthe individual components of the plasma processing apparatus 10 may becontrolled by the control unit Cnt.

Then, a process ST4 is performed in the method MT. In the process ST4,the wafer W is carried out into the atmospheric environment. For thepurpose, the wafer W is transferred by the transfer robot 116 r withinthe transfer module 116 into the load lock module 141 or the load lockmodule 142 from the processing vessel 12. Thereafter, the wafer W istransferred into the FOUP 122 by the transfer robot 112 r within theloader module 112.

Thereafter, a process ST5 is performed in the method MT. In the processST5, wet cleaning is performed on the wafer W. For the purpose, thewafer W is transferred into a wet cleaning apparatus 210 (see FIG. 3).For example, an organic solvent and/or an acidic solution is used as acleaning liquid in the process ST5. In the process ST5, the organic filmOM formed on the surface of the wafer W is peeled off by the wetcleaning. Further, the aforementioned copper fluoride and/or thereaction product on the metal mask MK are removed. Immediately after theprocess ST5, copper is filled in the via hole VH and the trench TR.

According to the method MT, the organic film OM is formed on the surfaceof the wafer W in the process ST3 after the diffusion barrier film DL isetched in the process ST2. The wafer W is transferred into theatmospheric environment after the process ST3, and, at this time, thesurface of the copper wiring CW and the surface of the metal mask MK areblocked by the organic film OM from the moisture in the atmosphere.Thus, according to the method MT, both the surface roughness of thecopper wiring CW and the surface roughness of the metal mask MK aresuppressed.

Below, the processing gas (second processing gas) used in the processST3 will be exemplified. The processing gas of a first example that canbe used in the process ST3 includes a hydrocarbon gas as thecarbon-containing gas. As the hydrocarbon gas, a methane gas (CH₄ gas)is used, for example. Further, the processing gas of the first examplemay further include a rare gas. Since the processing gas of the firstexample contains the hydrocarbon gas as the carbon-containing gas, theorganic film OM formed by the processing gas of the first example hardlycontains fluorine. Accordingly, the organic film OM has a high wettingproperty, i.e., a small contact angle with respect to the cleaningliquid used in the wet cleaning of the process ST5. Thus, the organicfilm OM is easily removed by the wet cleaning.

Further, the processing gas of the first example does not contain ahydrogen gas. The hydrogen gas is a source of active species of hydrogenhaving an effect of reducing the organic film OM. Since the processinggas of the first example contains no hydrogen gas, the organic film OMcan be formed efficiently.

The processing gas of a second example that can be used in the processST3 contains a fluorocarbon gas as the carbon-containing gas and ahydrogen gas. As the fluorocarbon gas contained in the processing gas ofthe second example, one or more of a C₄F₈ gas, a C₄F₆ gas and a C₅F₈ gasmay be used. Further, the processing gas of the second example mayfurther include a rare gas. A film containing fluorine and carbon isformed by the fluorocarbon gas, and the amount of the fluorine in thisfilm is reduced by active species of hydrogen generated from thehydrogen gas. Thus, by using the processing gas of the second example,the organic film OM having a small amount of fluorine is formed on thesurface of the wafer W.

In the processing gas of the second example, a flow rate of the hydrogengas may be set to be 5 times to 20 times as high as a flow rate of thefluorocarbon gas. By setting the flow rate of the hydrogen gas in thisrange, the organic film OM having a small amount of the fluorine can beformed.

In the exemplary embodiment, a temperature of the wafer W is maintainedat 60° C. or less in a period during which the process ST3 is performed.For the purpose, a coolant having a controlled temperature is suppliedinto the coolant path 24 from the chiller unit provided at the outsideof the processing vessel 12. Under a high-temperature environment equalto or higher than 300° C., thermal decomposition of the organic film OMmay occur. By maintaining the temperature of the wafer W at 60° C. orless, however, the thermal decomposition of the organic film OM issuppressed. Thus, according to the present exemplary embodiment, theorganic film OM can be formed efficiently.

Furthermore, in the exemplary embodiment, a processing condition of theprocess ST3, e.g., a processing time is adjusted such that a thicknessof the organic film OM is equal to or larger than 2 nm. With the organicfilm OM having the thickness equal to or larger than 2 nm, it may bepossible to suppress the moisture in the atmosphere from being contactedwith the organic film OM.

In addition, in the exemplary embodiment, over a period during which theprocess ST2 is performed and the period during which the process ST3 isperformed, the wafer W may be kept accommodated in the processing vessel12 of the single plasma processing apparatus 10. Alternatively, theprocess ST2 and the process ST3 may be performed by using individualplasma processing apparatuses.

In the above, the various exemplary embodiments have been described.However, the above-described exemplary embodiments are not limiting, andvarious changes and modifications may be made. By way of example, toperform the process ST1 to the process ST3 of the method MT, any ofvarious types of plasma processing apparatuses such as an inductivelycoupled plasma processing apparatus and a plasma processing apparatusconfigured to generate plasma by a surface wave such as a microwave maybe used.

Hereinafter, experiments conducted to evaluate the method MT will beexplained. Further, it should be noted that the present disclosure isnot limited to the experiments to be described below.

[Experiment for Evaluating Method MT Including the Process ST3 withProcessing Gas of First Example]

In this experiment, three wafers having the same structure as the waferW shown in FIG. 2 are prepared. The diffusion barrier film DL of eachwafer is formed of SiCN, and a film thickness thereof is 35 nm. Thesecond insulating film IS2 is made of SiOCH, and a film thicknessthereof is 150 nm. The oxide film OX is a silicon oxide film made ofTEOS, and a film thickness thereof is 20 nm. The metal mask MK is madeof TiN, and a film thickness thereof is 35 nm. A film thickness of theorganic layer OL is 230 nm. A film thickness of the antireflection filmAL is 35 nm. The resist mask RM has a film thickness of 75 nm. Further,in this experiment, samples 1 to 3 having the same structure as thewafer W shown in FIG. 11 are prepared from the three wafers byperforming the process ST1 in the plasma processing apparatus 10.

Subsequently, the process ST2 is performed on the sample 1 by using theplasma processing apparatus 10. For the sample 2, the process ST2 isperformed by using the plasma processing apparatus 10, and, afterperforming the process ST2, a plasma process is performed on the sample2 with a nitrogen gas and a hydrogen gas. Further, the process ST2 andthe process ST3 are performed on the sample 3 in the plasma processingapparatus 10. Then, the samples 1 to 3 are placed in the FOUP 122 for 24hours. Thereafter, a surface state of the metal mask MK of each sampleis observed by using an electron microscope, and a ratio (%)(hereinafter, referred to as “ratio of surface roughness of metal maskMK”) of an area of a portion of the metal mask MK on which the surfaceroughness is generated with respect to an entire surface area of themetal mask MK is calculated.

Further, as samples 4 to 6, blanket wafers having a copper layer of auniform thickness are prepared. For the sample 4, the process ST2 isperformed by using the plasma processing apparatus 10. The process ST2is performed on the sample 5 by using the plasma processing apparatus10, and, after performing the process ST2, a plasma process is performedon the sample 5 with a nitrogen gas and a hydrogen gas. Further, theprocess ST2 and the process ST3 are performed on the sample 6 by usingthe plasma processing apparatus 10. Then, the samples 4 to 6 are placedin the FOUP 122 for 24 hours. Thereafter, surface states of the samples4 to 6 are observed by using an electron microscope, and a ratio (%)(hereinafter, referred to as “ratio of surface roughness of copperlayer”) of an area of a portion of the copper layer of each of thesamples 4 to 6 on which the surface roughness is generated with respectto an entire surface area of the copper layer is calculated.

Further, as samples 7 to 9, there are prepared blanket wafers having aninsulating film which is made of SiOCH and has a uniform thickness areprepared. The process ST1 f and the process ST2 are performed on thesample 7 by using the plasma processing apparatus 10. For the sample 8,the process ST1 f and the process ST2 are performed by using the plasmaprocessing apparatus 10, and, then, a plasma process is performed on thesample 8 with a nitrogen gas and a hydrogen gas. For the sample 9, theprocess ST1 f and the process ST2 are performed by using the plasmaprocessing apparatus 10, and, then, the process ST3 is furtherperformed. Thereafter, the samples 7 to 9 are placed in the FOUP 122 for24 hours. Afterwards, each of the samples 7 to 9 is cut into two pieces,and one of the two pieces is processed by hydrofluoric acid of 0.1% for1 minute. Then, a difference (hereinafter, referred to as “damageamount”) between a thickness of the insulating film of the one piece anda thickness of the insulating film of the other piece is calculated as aparameter for evaluating the damage on the insulating film. If thedifference in the film thicknesses, that is, the damage amount is large,it may be deemed that the damage on the insulating film is large.

Further, as samples 10 to 12, silicon wafers are prepared. Only theprocess ST2 is performed on the sample 10 by using the plasma processingapparatus 10. For the sample 11, the process ST2 is performed by usingthe plasma processing apparatus 10, and, then, a plasma process isperformed with a nitrogen gas and a hydrogen gas. Further, for thesample 12, the process ST2 is performed by using the plasma processingapparatus 10, and, then, the process ST3 is further performed. Then, thesamples 10 to 12 are placed in the FOUP for 24 hours. Thereafter,contact angles of the samples 10 to 12 with respect to water aremeasured.

Below, processing conditions of individual processes in the experimentare specified.

<Process ST1 f>

Internal pressure of processing vessel 12: 70 mTorr (9.333 Pa)

Processing gas:

-   -   C₄F₈ gas: 40 sccm, CF₄ gas: 50 sccm, Ar gas: 1000 sccm, N₂ gas:        35 sccm, O₂ gas: 15 sccm

First high frequency power: 264 W

Second high frequency power: 106 W

<Process ST2>

Internal pressure of processing vessel 12: 70 mTorr (9.333 Pa)

Processing gas:

-   -   C₄F₈ gas: 40 sccm, CF₄ gas: 50 sccm, Ar gas: 1200 sccm, N₂ gas:        40 sccm, O₂ gas: 15 sccm

First high frequency power: 422 W

Second high frequency power: 53 W

<Process ST3>

Internal pressure of processing vessel 12: 50 mTorr (6.666 Pa)

Processing gas:

-   -   CH₄ gas: 20 sccm, Ar gas: 400 sccm

First high frequency power: 200 W

Second high frequency power: 0 W

<Plasma Process with Nitrogen Gas and Hydrogen Gas>

Internal pressure of processing vessel 12: 50 mTorr (6.666 Pa)

Processing gas:

-   -   N₂ gas: 200 sccm, H₂ gas: 100 sccm

First high frequency power: 400 W

Second high frequency power: 100 W

Now, experiment results will be explained. The ratio of the surfaceroughness of the metal mask MK of the sample 1 is 0%. Further, the ratioof the surface roughness of the copper layer of the sample 4 is 100%.From this result, it is found out that surface roughness of the copperlayer is generated if a wafer, on which the process ST2 is performed andno process is performed thereafter, is placed in the atmosphericenvironment.

The ratio of the surface roughness of the metal mask MK of the sample 2is 80%. Further, the ratio of the surface roughness of the copper layerof the sample 5 is 0%. From this result, it is found out that, byperforming the plasma process with the N₂ gas and the H₂ gas afterperforming the process ST2, the surface roughness of the metal mask MKis generated, whereas the surface roughness of the copper layer can besuppressed.

Further, the ratio of the surface roughness of the metal mask MK of thesample 3 is 0%. Further, the ratio of the surface roughness of thecopper layer of the sample 6 is 0%. From this result, it is found outthat the surface roughness of the copper layer and the surface roughnessof the metal mask MK can both be suppressed by performing the processST3 after performing the process ST2.

In addition, as a result of measuring the thickness of the organic filmOM formed in the process ST3, the thickness is found to be 2 nm. Thus,it is found out that, if the thickness of the organic film OM is equalto or larger than 2 nm, the moisture contained in the atmosphere cannotpermeate the organic film OM, so that the copper layer and the metalmask MK are protected.

Further, the damage amounts of the samples 7 to 9 are found to be 3.0nm, 8.2 nm and 1.7 nm, respectively. From this result, it is found outthat the damage on the insulating film caused by performing the processST3 is small.

Additionally, the contact angles of the surfaces of the samples 10 to 12with respect to the water are found to be 73.1°, 53.1° and 65.4°,respectively. Considering that the contact angle of the surface of thesample 12 with respect to the water is much smaller than 90°, it isfound out that the organic film OM formed through the process ST3 has ahigh wetting property.

[Experiment for Evaluating Processing Conditions of Process ST3]

In this experiment, four wafers having the same structure as the wafer Wshown in FIG. 2 are prepared. The diffusion barrier film DL of eachwafer is formed of SiCN, and a film thickness thereof is 35 nm. Thesecond insulating film IS2 is made of SiOCH, and a film thicknessthereof is 150 nm. The oxide film OX is a silicon oxide film made ofTEOS, and a film thickness thereof is 20 nm. The metal mask MK is madeof TiN, and a film thickness thereof is 35 nm. A film thickness of theorganic layer OL is 230 nm. A film thickness of the antireflection filmAL is 35 nm. Further, the resist mask RM has a film thickness of 75 nmand has a line-and-space pattern. By performing the process ST1 in theplasma processing apparatus 10, samples 13 to 16 having the samestructure as the wafer W shown in FIG. 11 are prepared from the fourwafers. The process ST2 and the process ST3 are performed on each of thesamples 13 to 16 by using the plasma processing apparatus 10. Then, thesamples 13 to 16 are placed in the FOUP 122 for 24 hours.

Further, as samples 17 to 20, blanket wafers having a copper layer of auniform thickness are prepared. The process ST1 f, the process ST2 andthe process ST3 are performed on each of the samples 17 to 20 by usingthe plasma processing apparatus 10. Then, the samples 17 to 20 areplaced in the FOUP 122 for 24 hours. Further, as samples 21 to 24, thereare prepared blanket wafers each having an insulating film which is madeof SiOCH and has a uniform thickness, and the process ST1 f, the processST2 and the process ST3 are performed on each of the samples 21 to 24 byusing the plasma processing apparatus 10. Then, the samples 21 to 24 areplaced in the FOUP 122 for 24 hours.

Below, processing conditions of the process ST1 f, the process ST2 andthe process ST3 are specified.

<Process ST1 f>

Internal pressure of processing vessel 12: 70 mTorr

Processing gas:

-   -   C₄F₈ gas: 40 sccm, CF₄ gas: 50 sccm, Ar gas: 1000 sccm, N₂ gas:        35 sccm, O₂ gas: 15 sccm

First high frequency power: 264 W

Second high frequency power: 106 W

<Process ST2>

Internal pressure of processing vessel 12: 70 mTorr (9.333 Pa)

Processing gas:

-   -   C₄F₈ gas: 40 sccm, CF₄ gas: 50 sccm, Ar gas: 1200 sccm, N₂ gas:        40 sccm, O₂ gas: 15 sccm

First high frequency power: 422 W

Second high frequency power: 53 W

<Process ST3>

Processing gas:

-   -   CH₄ gas: 20 sccm, Ar gas: 400 sccm

Further, in the process ST3 performed on the sample 13, the sample 17and the sample 21, the internal pressure of the processing vessel 12 isset to be 100 mTorr (13.33 Pa), and the first high frequency power andthe second high frequency power are set to be 200 W and 0 W,respectively. Furthermore, in the process ST3 performed on the sample14, the sample 18 and the sample 22, the internal pressure of theprocessing vessel 12 is set to be 200 mTorr (26.66 Pa), and the firsthigh frequency power and the second high frequency power are set to be200 W and 0 W, respectively. Furthermore, in the process ST3 performedon the sample 15, the sample 19 and the sample 23, the internal pressureof the processing vessel 12 is set to be 100 mTorr (13.33 Pa), and thefirst high frequency power and the second high frequency power are setto be 100 W and 0 W, respectively. In addition, in the process ST3performed on the sample 16, the sample 20 and the sample 24, theinternal pressure of the processing vessel 12 is set to be 100 mTorr(13.33 Pa), and the first high frequency power and the second highfrequency power are set to be 400 W and 0 W, respectively.

The ratios of the surface roughness of the metal masks MK of the samples13 to 16 are calculated, and it is found out that no surface roughnessis generated on the metal mask MK of all of these samples. Thus, it isfound out that, through the process ST3, the surface roughness of themetal mask MK can be suppressed regardless of the processing conditionsinvolved.

Further, the ratios of the surface roughness of the copper layers of thesamples 17 to 20 are calculated, and it is found out that no surfaceroughness is generated on the copper layers of the samples 17 to 19. Asstated above, in the process ST3 performed on the samples 17 to 19, thefirst high frequency power is set to be equal to or less than 200 W.Meanwhile, the ratio (%) of the surface roughness of the copper layer ofthe sample 20 is found to be 15%, though this ratio is not high. Asstated above, in the process ST3 performed on the sample 20, the firsthigh frequency power is set to be 400 W. As can be seen from thisresult, in the process ST3, it is found out that it is desirable to setthe first high frequency power to 200 W or less.

Furthermore, the damage amounts of the insulating films of the samples21 to 24 are calculated. As a result, the damage amounts of theinsulating films of the samples 21 to 24 are found to be 1.7 nm, 7.0 nm,3.7 nm and 4.0 nm, respectively. As stated above, in the process ST3performed on the sample 21, the sample 23 and the sample 24, theinternal pressure of the processing vessel 12 is set to be equal to orless than 100 mTorr. Further, in the process ST3 performed on the sample22, the internal pressure of the processing vessel 12 is set to be 200mTorr. As a result, in the process ST3, it is found out that it isdesirable to set the internal pressure of the processing vessel 12 to beequal to or less than 100 mTorr (13.33 Pa).

[Experiment for Evaluating Method MT Including Process ST3 withProcessing Gas of Second Example]

In this experiment, three wafers having the same structure as the waferW shown in FIG. 2 are prepared. The diffusion barrier film DL of eachwafer is formed of SiCN, and a film thickness thereof is 35 nm. Thesecond insulating film IS2 is made of SiOCH, and a film thicknessthereof is 150 nm. The oxide film OX is a silicon oxide film made ofTEOS, and a film thickness thereof is 20 nm. The metal mask MK is madeof TiN, and a film thickness thereof is 35 nm. A film thickness of theorganic layer OL is 230 nm. A film thickness of the antireflection filmAL is 35 nm. The resist mask RM has a film thickness of 75 nm. Byperforming the process ST1 in the plasma processing apparatus 10,samples 25 to 27 having the same structure as the wafer W shown in FIG.11 are prepared from the three wafers. Then, the process ST2 and theprocess ST3 are performed on each of the samples 25 to 27 by using theplasma processing apparatus 10. Thereafter, the samples 25 to 27 areplaced in the FOUP 122 for 24 hours.

Further, as samples 28 to 30, blanket wafers having a copper layer of auniform thickness are prepared, and the process ST1 f, the process ST2and the process ST3 are performed on each of the samples 28 to 30 byusing the plasma processing apparatus 10. Thereafter, the samples 28 to30 are placed in the FOUP 122 for 24 hours. Furthermore, as samples 31to 33, there are prepared blanket wafers having an insulating film whichis made of SiOCH and has a uniform thickness, and the process ST1 f, theprocess ST2 and the process ST3 are performed on each of the samples 31to 33 by using the plasma processing apparatus 10. Thereafter, thesamples 31 to 33 are placed in the FOUP 122 for 24 hours. In addition,as samples 34 to 36, silicon wafers are prepared, and the process ST2and the process ST3 are performed on each of the samples 34 to 36 byusing the plasma processing apparatus 10. Thereafter, the samples 34 to36 are placed in the FOUP 122 for 24 hours.

Below, processing conditions of the process ST1 f, the process ST2 andthe process ST3 are specified.

<Process ST1 f>

Internal pressure of processing vessel 12: 70 mTorr

Processing gas:

-   -   C₄F₈ gas: 40 sccm, CF₄ gas: 50 sccm, Ar gas: 1000 sccm, N₂ gas:        35 sccm, O₂ gas: 15 sccm

First high frequency power: 264 W

Second high frequency power: 106 W

<Process ST2>

Processing gas:

-   -   C₄F₈ gas: 40 sccm, CF₄ gas: 50 sccm, Ar gas: 1200 sccm, N₂ gas:        40 sccm, O₂ gas: 15 sccm

First high frequency power: 422 W

Second high frequency power: 53 W

<Process ST3>

Internal pressure of processing vessel 12: 50 mTorr (6.666 Pa)

First high frequency power: 200 W

Second high frequency power: 0 W

In the process ST3 performed on the sample 25, the sample 28, the sample31 and the sample 34, a flow rate of the C₄F₈ gas, a flow rate of the Argas and a flow rate of the hydrogen gas (H₂ gas) are set to be 20 sccm,400 sccm and 0 sccm, respectively. Further, in the process ST3 performedon the sample 26, the sample 29, the sample 32 and the sample 35, theflow rate of the C₄F₈ gas, the flow rate of the Ar gas and the flow rateof the hydrogen gas are set to be 20 sccm, 400 sccm and 100 sccm,respectively. Furthermore, in the process ST3 performed on the sample27, the sample 30, the sample 33 and the sample 36, the flow rate of theC₄F₈ gas, the flow rate of the Ar gas and the flow rate of the hydrogengas are set to be 20 sccm, 400 sccm and 200 sccm, respectively.

The ratios of the surface roughness of the metal masks MK of the samples25 to 27 are calculated, and it is found out that no surface roughnessis generated on the metal mask MK of all of these samples. Thus, it isfound out that the process ST3 with the processing gas containing thefluorocarbon gas is capable of suppressing the surface roughness of themetal mask MK.

Further, the ratios of the surface roughness of the metal layers of thesamples 28 to 30 are calculated, and it is found out that no surfaceroughness is generated on the copper layers of the samples 28 to 30.Thus, it is found out that the process ST3 with the processing gascontaining the fluorocarbon gas is capable of suppressing the surfaceroughness of the copper layer.

Furthermore, the damage amounts of the insulating films of the samples31 to 33 are calculated. As a result, the damage amounts of theinsulating films of the samples 31 to 33 are found to be 0.3 nm, 0.7 nmand 3.7 nm, respectively. From this result, it is found out that damageof the insulating film can be suppressed in the process ST3 with theprocessing gas containing the fluorocarbon gas.

In addition, the contact angles of the samples 34 to 36 with respect towater are calculated. As a result, the contact angles of the samples 34to 36 with respect to the water are found to be 100.3°, 69.6° and 56.6°,respectively. From this result, by including the hydrogen gas in theprocessing gas used in the process ST3, it is found out that the wettingproperty of the organic film OM formed through the process ST3 can beimproved. It is also found out that it is desirable to set the flow rateof the hydrogen gas to be 5 times to 20 times as large as the flow rateof the fluorocarbon gas.

From the foregoing, it will be appreciated that various embodiments ofthe present disclosure have been described herein for purposes ofillustration, and that various modifications may be made withoutdeparting from the scope and spirit of the present disclosure.Accordingly, the various embodiments disclosed herein are not intendedto be limiting.

We claim:
 1. A method of processing a target object, comprising:preparing the target object, including a wiring layer having a firstinsulating film and a copper wiring formed in the first insulating film,a diffusion barrier film provided on the wiring layer, a secondinsulating film provided on the diffusion barrier film and a metal maskwhich is provided on the second insulating film and provided with anopening, in which a portion of the second insulating film exposedthrough the opening is etched; generating plasma of a first processinggas containing a fluorocarbon gas and/or a hydrofluorocarbon gas to etchthe diffusion barrier film until the copper wiring is exposed; andgenerating plasma of a second processing gas containing acarbon-containing gas to form an organic film on a surface of the targetobject in which the diffusion barrier film is etched.
 2. The method ofclaim 1, wherein the carbon-containing gas is a hydrocarbon gas.
 3. Themethod of claim 2, wherein the second processing gas does not contain ahydrogen gas.
 4. The method of claim 1, wherein the carbon-containinggas is a fluorocarbon gas, and the second processing gas furthercontains a hydrogen gas.
 5. The method of claim 4 wherein a flow rate ofthe hydrogen gas is set to be 5 times to 20 times as large as a flowrate of the fluorocarbon gas contained in the second processing gas. 6.The method of claim 4, wherein the second processing gas contains one ormore of a C₄F₈ gas, a C₄F₈ gas and a C₅F₈ gas as the fluorocarbon gascontained in the second processing gas.
 7. The method of claim 1,wherein a temperature of the target object is maintained at 60° C. orless in the generating of the plasma of the second processing gas. 8.The method of claim 1, wherein the organic film having a film thicknessequal to or larger than 2 nm is formed in the generating of the plasmaof the second processing gas.
 9. The method of claim 1, wherein thefirst processing gas contains one or more of a CF₄ gas, a CHF₃ gas, aC₄F₈ gas, a C₄F₆ gas, a CH₂F₂ gas and a CH₃F gas.
 10. The method ofclaim 1, wherein the diffusion barrier film includes a single-layeredfilm made of SiC, SiCN or SiN, or a multi-layered film including aplurality of films each of which is made of SiC, SiCN or SiN.
 11. Themethod of claim 1, wherein the second insulating film includes asingle-layered film made of SiOCH, a multi-layered film including a filmmade of SiO₂ and a low dielectric constant film, or a multi-layered filmincluding a plurality of low dielectric constant films.
 12. The methodof claim 1, wherein the metal mask is made of Ti or TiN.
 13. The methodof claim 1, wherein the target object is kept accommodated in aprocessing vessel of a single plasma processing apparatus over a periodduring which the generating of the plasma of the first processing gas isperformed and a period during which the generating of the plasma of thesecond processing gas is performed.